1/* vi: set sw=4 ts=4: */
2/* mkswap.c - format swap device (Linux v1 only)
3 *
4 * Copyright 2006 Rob Landley <rob@landley.net>
5 *
6 * Licensed under GPL version 2, see file LICENSE in this tarball for details.
7 */
8#include "libbb.h"
9
10#if ENABLE_SELINUX
11static void mkswap_selinux_setcontext(int fd, const char *path)
12{
13	struct stat stbuf;
14
15	if (!is_selinux_enabled())
16		return;
17
18	if (fstat(fd, &stbuf) < 0)
19		bb_perror_msg_and_die("fstat failed");
20	if (S_ISREG(stbuf.st_mode)) {
21		security_context_t newcon;
22		security_context_t oldcon = NULL;
23		context_t context;
24
25		if (fgetfilecon(fd, &oldcon) < 0) {
26			if (errno != ENODATA)
27				goto error;
28			if (matchpathcon(path, stbuf.st_mode, &oldcon) < 0)
29				goto error;
30		}
31		context = context_new(oldcon);
32		if (!context || context_type_set(context, "swapfile_t"))
33			goto error;
34		newcon = context_str(context);
35		if (!newcon)
36			goto error;
37		/* fsetfilecon_raw is hidden */
38		if (strcmp(oldcon, newcon) != 0 && fsetfilecon(fd, newcon) < 0)
39			goto error;
40		if (ENABLE_FEATURE_CLEAN_UP) {
41			context_free(context);
42			freecon(oldcon);
43		}
44	}
45	return;
46 error:
47	bb_perror_msg_and_die("SELinux relabeling failed");
48}
49#else
50# define mkswap_selinux_setcontext(fd, path) ((void)0)
51#endif
52
53/* from Linux 2.6.23 */
54/*
55 * Magic header for a swap area. ... Note that the first
56 * kilobyte is reserved for boot loader or disk label stuff.
57 */
58struct swap_header_v1 {
59/*	char     bootbits[1024];    Space for disklabel etc. */
60	uint32_t version;        /* second kbyte, word 0 */
61	uint32_t last_page;      /* 1 */
62	uint32_t nr_badpages;    /* 2 */
63	char     sws_uuid[16];   /* 3,4,5,6 */
64	char     sws_volume[16]; /* 7,8,9,10 */
65	uint32_t padding[117];   /* 11..127 */
66	uint32_t badpages[1];    /* 128 */
67	/* total 129 32-bit words in 2nd kilobyte */
68} FIX_ALIASING;
69
70#define NWORDS 129
71#define hdr ((struct swap_header_v1*)bb_common_bufsiz1)
72
73struct BUG_sizes {
74	char swap_header_v1_wrong[sizeof(*hdr)  != (NWORDS * 4) ? -1 : 1];
75	char bufsiz1_is_too_small[COMMON_BUFSIZE < (NWORDS * 4) ? -1 : 1];
76};
77
78/* Stored without terminating NUL */
79static const char SWAPSPACE2[sizeof("SWAPSPACE2")-1] ALIGN1 = "SWAPSPACE2";
80
81int mkswap_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
82int mkswap_main(int argc UNUSED_PARAM, char **argv)
83{
84	int fd;
85	unsigned pagesize;
86	off_t len;
87	const char *label = "";
88
89	opt_complementary = "-1"; /* at least one param */
90	/* TODO: -p PAGESZ, -U UUID */
91	getopt32(argv, "L:", &label);
92	argv += optind;
93
94	fd = xopen(argv[0], O_WRONLY);
95
96	/* Figure out how big the device is */
97	len = get_volume_size_in_bytes(fd, argv[1], 1024, /*extend:*/ 1);
98	pagesize = getpagesize();
99	len -= pagesize;
100
101	/* Announce our intentions */
102	printf("Setting up swapspace version 1, size = %"OFF_FMT"u bytes\n", len);
103	mkswap_selinux_setcontext(fd, argv[0]);
104
105	/* hdr is zero-filled so far. Clear the first kbyte, or else
106	 * mkswap-ing former FAT partition does NOT erase its signature.
107	 *
108	 * util-linux-ng 2.17.2 claims to erase it only if it does not see
109	 * a partition table and is not run on whole disk. -f forces it.
110	 */
111	xwrite(fd, hdr, 1024);
112
113	/* Fill the header. */
114	hdr->version = 1;
115	hdr->last_page = (uoff_t)len / pagesize;
116
117	if (ENABLE_FEATURE_MKSWAP_UUID) {
118		char uuid_string[37];
119		generate_uuid((void*)hdr->sws_uuid);
120		printf("UUID=%s\n", unparse_uuid((uint8_t *)hdr->sws_uuid, uuid_string));
121	}
122	safe_strncpy(hdr->sws_volume, label, 16);
123
124	/* Write the header.  Sync to disk because some kernel versions check
125	 * signature on disk (not in cache) during swapon. */
126	xwrite(fd, hdr, NWORDS * 4);
127	xlseek(fd, pagesize - 10, SEEK_SET);
128	xwrite(fd, SWAPSPACE2, 10);
129	fsync(fd);
130
131	if (ENABLE_FEATURE_CLEAN_UP)
132		close(fd);
133
134	return 0;
135}
136